WASHINGTON — The Trump administration on Thursday revoked a scientific finding that long has been the central basis for U.S. action to regulate greenhouse gas emissions and fight climate change, the most aggressive move by the Republican president to roll back climate regulations.

The rule finalized by the Environmental Protection Agency rescinds a 2009 government declaration known as the endangerment finding that determined that carbon dioxide and other greenhouse gases threaten public health and welfare. The Obama-era finding is the legal underpinning of nearly all climate regulations under the Clean Air Act for motor vehicles, power plants and other pollution sources that are heating the planet.

The repeal eliminates all greenhouse gas emissions standards for cars and trucks and could unleash a broader undoing of climate regulations on stationary sources such as power plants and oil and gas facilities, experts say. Legal challenges are near certain.

President Donald Trump called the move “the single largest deregulatory action in American history, by far,” while EPA Administrator Lee Zeldin called the endangerment finding “the Holy Grail of federal regulatory overreach.”

Trump called the endangerment finding “one of the greatest scams in history,” claiming falsely that it “had no basis in fact” or law. “On the contrary, over the generations, fossil fuels have saved millions of lives and lifted billions of people out of poverty all over the world,” Trump said at a White House ceremony, although scientists across the globe agree that carbon dioxide and other greenhouse gases are driving catastrophic heat waves and storms, droughts and sea level rise.

Environmental groups described the move as the single biggest attack in U.S. history against federal authority to address climate change. Evidence backing up the endangerment finding has only grown stronger in the 17 years since it was approved, they said.

“This action will only lead to more climate pollution, and that will lead to higher costs and real harms for American families,” said Fred Krupp, president of Environmental Defense Fund, adding that the consequences would be felt on Americans’ health, property values, water supply and more.

The EPA also said it will propose a two-year delay to a Biden-era rule restricting greenhouse gas emissions by cars and light trucks. And the agency will end incentives for automakers who install automatic start-stop ignition systems in their vehicles. The device is intended to reduce emissions, but Zeldin said “everyone hates” it.

Zeldin, a former Republican congressman who was tapped by Trump to lead EPA last year, has criticized his predecessors in Democratic administrations, saying that in the name of tackling climate change, they were “willing to bankrupt the country.”

The endangerment finding “led to trillions of dollars in regulations that strangled entire sectors of the United States economy, including the American auto industry,” Zeldin said. “The Obama and Biden administrations used it to steamroll into existence a left-wing wish list of costly climate policies, electric vehicle mandates and other requirements that assaulted consumer choice and affordability.”